The goal of this proposal is to address the urgent need for asthma patients by taking advantage of the recent breakthroughs in the field of Ca2+ signaling to benefit asthma therapy. Multiple lines of evidence suggest an important role for CRAC (Ca2+-release-activated Ca2+) channels in asthma. Ca2+ entry via CRAC channels is a predominant mechanism of intracellular Ca2+ elevation in T cells and mast cells that are important players in airway allergic inflammation. Recently, we and others identified Orai1 (CRACM1, TMEM142) as a long-sought pore component of CRAC channels. Discovery of CRAC channel components provides a new opportunity to develop asthma therapy by targeting CRAC channels to suppress the functions of TH2 cells. In this proposal, we will test this possibility using two novel and strong experimental tools- Orai1 conditional knockout mice with T cell- specific deletion of Orai1, and small molecule blockers of Orai1 that we have recently identified from high throughput chemical library screenings. Our studies will first examine the function of Orai1 in differentiation of TH2 cells and in asthma using conditionally targeted Orai1 knockout mice (Aim 1). We will check how the deficiency of Orai1 will influence the transcriptional programs for TH2 differentiation. We will also determine the role of Orai1 using an animal model of asthma by measuring lung functions (e.g. lung resistance and dynamic compliance). We then correlate the obtained basic knowledge with identification of novel therapeutic methods to treat asthma using small molecule blockers of Orai1 (Aim 2). Using specific blockers, we also plan to determine the role of Orai1 in the functions of B cells and mast cells. The proposed studies are conceptually and technically novel and innovative because we will be the first to test the therapeutic potential of blocking Orai1 in the disease settings of asthma using unique tools we have established. Thus, our studies will have a broad impact on basic understanding of the function of Ca2+ signaling in allergic T cells, its role in other allergc cell functions (e.g. B cells, mast cells, type 2 innate immune cells), and development of novel therapy to treat severe forms of allergic and atopic inflammatory diseases.